(1) Field of the Invention
The invention relates to a magnetic coupling pump, and more particularly, to a magnetic coupling pump, used as a water pump, to contemplate enhancement of cooling efficiency for exothermic electronic parts mounted on a circuit board as well as improvement of detection accuracy of a magnetism detecting element mounted on the circuit board.
(2) Description of the Prior Art
As is well-known, a magnetic coupling pump used as a water pump is constructed such that a partition partitions off a motor chamber and a pump chamber, through which a cooling water flows, a rotor is disposed in the pump chamber, and a stator (motor) is disposed in the motor chamber.
As an example of conventional magnetic coupling pumps, there has been known a magnetic coupling pump, as disclosed in FIG. 2 of Japanese Patent Laid-Open No. 311290/1998, constructed such that a circuit board is disposed in a motor chamber to be in parallel to an end surface of a rotor, exothermic electronic parts, such as power transistors or the like, for driving a motor, are mounted on a remaining portion of the circuit board facing the end surface of the rotor, and the exothermic electronic parts are cooled by a cooling water through a partition.
Also, among conventional magnetic coupling pumps, there has been known a magnetic coupling pump constructed such that a Hall element as a magnetism detecting element for detecting a rotating angle position of a rotor is mounted on that portion of a circuit board, which faces a magnet portion of the rotor, in order to control timing of energization of a motor, in other words, to control the switching action of power transistors or the like.
Further, there has been known a magnetic coupling pump of that type, in which both the above exothermic electronic parts and the above magnetism detecting element are mounted on a circuit board.
However, with a magnetic coupling pump of the above-mentioned type, in which both the above exothermic electronic parts and the above magnetism detecting element are mounted on a circuit board, the exothermic electronic parts and the magnetism detecting element are arranged comparatively close to each other, so that the magnetism detecting element is susceptible to thermal damage from the exothermic electronic parts. Also, since the exothermic electronic parts are larger in thickness than the magnetism detecting element, an air gap between the magnetism detecting element and a partition is comparatively large, which restricts detection accuracy of the magnetism detecting element.
The invention has its object to solve the above-mentioned problems of the prior art and to contemplate enhancement of cooling efficiency for exothermic electronic parts as well as improvement of detection accuracy of a magnetism detecting element.
To attain the above object, a magnetic coupling pump according to the invention has a feature in comprising a partition partitioning off a motor chamber and a pump chamber, through which a cooling water flows, a substantially cylindrical-cup shaped rotor disposed in the pump chamber, a circuit board disposed in the motor chamber to be in parallel to an annular-shaped end surface of the rotor, a magnetism detecting element mounted on that portion of the circuit board, which faces a magnet portion of the rotor, and exothermic electronic parts mounted on the remaining portion of the circuit board, wherein a thickness of an annular-shaped wall portion of the partition facing the annular-shaped end surface of the rotor is made thin in a portion adjacent to the exothermic electronic parts on condition that an annular-shaped surface of the annular-shaped wall portion on a side of the annular-shaped end surface of the rotor is a non-inclined flat surface, and wherein the magnetism detecting element and the exothermic electronic parts, respectively, are arranged in opposite positions in a substantially annular-shaped area of the circuit board, which faces the annular-shaped end surface of the rotor.
In the above-mentioned manner, the annular-shaped wall portion is made thin in wall thickness, whereby the exothermic electronic parts are efficiently cooled by a cooling water, thus enabling suppressing thermal damage, which the magnetism detecting element suffers from heat generated by the exothermic electronic parts.
Also, the magnetism detecting element and the exothermic electronic parts, respectively, are arranged in substantially opposite positions in the substantially annular-shaped area of the circuit board, so that a spacing between the magnetism detecting element and the exothermic electronic parts becomes large to enable suppressing thermal damage, which the magnetism detecting element suffers from heat generated by the exothermic electronic parts.
Also, the circuit board can be made to approach the annular-shaped wall portion by a distance corresponding to reduction in wall thickness of the annular-shaped wall portion, with the result that a distance from the magnetism detecting element to an end surface of the annular-shaped wall portion on the side of the motor chamber becomes small and so a spacing between the annular-shaped end surface of the rotor and the magnetism detecting element decreases. Therefore, the magnetism detecting element is increased in detection level to be enhanced in accuracy of detection.